The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Operation of cranes and other payload handling apparatuses such as harbour cranes are increasingly automated. With increasing automation, number of personnel moving within the operating areas of the payload handling apparatuses is decreased. In a fully automated operating area, there may be no people moving in the area under normal circumstances. It is also possible that there are many automated payload handling apparatuses moving in the area. In such highly automated operating areas those areas, where personnel are allowed to move without risking their safety, may be marked to the ground. It is also possible that the handling of the payload may be stopped during the time people are moving in the area, e.g. to perform maintenance.
Safety for handling payload may be provided by sensors for detecting the people moving in the payload handling area. These sensors aid in the automated payload handling apparatuses to adjust their operation for providing safety. However, the people in the operating area have to stay in the marked areas or have faith that the sensors detect them and cause the payload handling apparatuses to adjust their operation to ensure safety.
When a harbour crane is under maintenance, it is out of production, whereby it is not in efficient use. However, in terms of economy, the downtime of an expensive apparatus like a harbour crane should be kept as rare and short as possible. Therefore, it is desirable that breaks in the operation of production machines are as short as possible. By scheduling the production breaks, it is possible to shorten the downtime, as the maintenance work can be planned better.
On the other hand even if the harbour crane is maintained as scheduled, it is possible that the scheduled maintenance is not sufficient and the harbour crane becomes inoperative or its operation is limited in between the scheduled maintenances. Such may be due to conditions of the operating environment causing an increased need for maintenance or due to the harbour crane being used in an abnormal way, e.g. for lifting very heavy loads. The unscheduled maintenances are unexpected to the skilled maintenance personnel who are few and may have pre-scheduled maintenance work in various countries for several weeks ahead. Thereby, there is likely to be delay involved in the maintenance personnel arriving to perform the unscheduled maintenance.